Cathode structure for vapor-converters.



S. W. FARNSWORTH. CATH ODE STRUCTURE FOR VAPOR CONVERTERS APPLICATION FILED MAY 3. 1916.

1 ;,%53 ,Q2. Patented J an. 15, 1918.

WITNESSES: 2/ INVENTOR ATT ORNY

unrrnn saunas PATENT ornrca SIDNEY W. FARNSWORTH, 0F PITTSBURGH, PENNSYLVANIA, .A-SSIGNOR T0 WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

CATHODE STRUCTURE FOR VAPOR-CONVERTERS.

lPatented Jams, rare.

Application filed May 3, 1916. Serial No. 95,071.

To all whom it may concern:

Be'it known that I, SIDNEY W. FARNS- WORTH, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Cathode Structures for Vapor-Converters, of whichthe following is'a specification.

My invention relates to electrode structures for vapor converters, and it has for its fobjectto provide means whereby a starting and maintaining arc may be readily initi- "ated in apparatus of the character designated and may thereafter be so supported as to operate effectively in maintalning the factivity of the cathode, with the consump-' tion of only a comparatively small amount of energy.

I Other objects of my invention will hereinafter more fully appear.

In the accompanying drawing, Figure 1 is side view, partially in section and partially in elevation, of a vapor converter embodylng a preferred form of my invention; Fig. 2 is a plan view of a keep-alive grid employed in connection with my invention','and Fig. 3 is a side view, partially in section and partially, in elevation, of the grid structure shown in Fig. 2.

In the operation of vapor converters, particularly those of the single-phase type, it is necessary to provide means for maintaining the activity of the cathode during those times when the voltage of the alternatingcurrent supply is less than the back electromotive force of the vapor arc. Various expedients have been proposed for performing this function, one of which is the use of a small auxiliary keep-alive anode that is suitably energized to maintain a direct-current arc to the cathode, thus supplying the de sired electron emission at all times.

There is a marked tendency in vapor converters, particularly when operating on relatively light loads, for the arc to concentrate .at a clearly defined spot on the cathode surfrom causes an undue elongation of the keepalive arc, resulting in an unnecessary consumption of energy thereby and also causing instability of operation.

In my copending application, Serial No. 39,796, filed July 14:, 1915, I propose the use of an extended conducting grid as a keepalive electrode, said grid being supported in proximity to the cathode surface and being substantially coextensive with the active portion thereof. A keep-alive arc is initiated by any suitable means, preferably by a small plunger which is adapted to make contact with the cathode, and said are is thereafter transferred to said grid and operates'therefrom to the cathode surface. Any movement of the main cathode spot causes the point of incidence of the keep-alive are upon said grid to move in consonance because of the inherent self-sh0rtening tendency of the arc. Thus, the keep-alive arc is at all times maintained at a minimum length, as is desired for economy and stability 'of operation.

In the. structure disclosed in the afore-* mentioned application, the grid is shown as a unitary structure, extending over the entire active cathode surface, as determined by the usual cathode ring. I find that, in operation, particularly under heavy loads, there is a tendency for localized heating in said grid, causing a severe warping thereof, even to such an extent as to cause contact between the grid and the cathode surface, with resultant short circuiting and extinguishment of the cathode arc. By the present invention, I provide a structure which is similar in function to that described in the aforementioned application but I provide a grid of conducting material which is divided into aplurality of small sectors or other coacting shapes, whereby local heating may take place with but little distortion of the grid, as a whole;

Referring to the drawing for a more de tailed understanding .of my invention, I show the container of a vapor converter at 4 in Fig. 1. Said container is provided with main anodes 5 and 6, a cathode 7 composed preferably, of a vaporizable reconstructing material, such, for example, as mercury or -a suitable amalgam and with a keep-alive ported from an armature member 9 which is under the influence of a solenoid 10, preferably mounted exterior to the container.

of the cathode spot thereof is Energy may be supplied to the plunger 8 from an exterior lead 11 through a stem 12, which is insulated from the container, and through a spring 13. A refractory insulating ring 14 rests in the cathode pool 7 for preventing the are from-impinging upon the container walls, and said ring supports, on its upper portion, a frame structure 15 of of any suitable form. As shown, the frame 15 comprises a strip of iron or other su1table material bent to form fou outwardly extending loops or lobes at the outer ends of which are carried screws 16 or other suitable means for attachment to the ring 14:. An upwardly extending bridge member 17 ismounted upon the frame 15 and is provided with a large centrally disposed opening 18 through which the plunger 8 extends into proximity to the cathode pool 7. The bridge member 17 is also provided with a small opening 19 into which is connected a fixed conductor 20 which is preferably so fastened to the stem 12 as to energize the entire frame structure from the supply lead 11. A grid structure 21 is supported from the frame 15 by any suitable means, such, for example, as welds indicated at 2:222,

and is substantially coextensive with the en tire active cathode surface, as determined by the ring 14:. The grid structure 21 is divided into quadrants by slits 23-23 so that severe local heating in any portion thereof causes expansion of that particular quadrant or sector but does not tend to warp or distort the grid, as a whole.

The method of starting a vapor converter embodying my invention is as follows. The anodes 5 and 6 being connected to the terminals of a source of alternating current to be rectified, direct current is supplied to the lead'll, and the solenoid 12 is energized from any suitable direct-current source (not shown). The armature 9, which has been occupying its lowermost position under the influence of gravity, is thereby drawn up, and the lower end of the plunger 8 is withdrawn from the cathode 7, striking a small The armature 9- direct-current are thereto. is drawn up so that the lower end of the plunger 8 reaches the level ofthe grid 21-21, whereupon the keep-alive arc transfers itself to said grid and current flows thereto, via the conductor 20. The electron emission from the main cathode initiates the main power are, and the travel followed by a travel of the small keep-alive are, as hereinbefore explained.

While I have shown my invention in its preferred form, it will be obvious to those skilled in the art that it is susceptible of various minor changes and modifications without departin from the spirit thereof, and I desire, therefore, that only such limitatmns shall be placed thereupon as are imposed by the prior art or as are indicated. in the ap pended claims. I

I claim as my invention: v

1. In vapor electric apparatus, the combination with a closed container, of a vaporizable reconstructing cathode therein, an auxiliary anode, means for striking an are between said twoelectrodes, and a multisection perforated conducting member mounted adjacent to said cathode and inconductive connection with said anode for subsequently supporting said are.

2. In vapor electric apparatus, the combination with a closed container, of a vaporizable reconstructing cathode therein, an auxiliary anode, means for striking an are between said two electrodes, and a' multi-section perforated conducting member mounted adjacent to said cathode substantially coextensive therewith and in conductive connection with said anode for subsequently supporting said are.

3. The combination with a vapor electric Y device embodying a closed container inclosmg a vaporizable reconstructing cathode 1. A maintaining electrode for vapor electric apparatus comprising a mechanically subdivided grid of conducting material.

' 5. A maintaining electrode for vapor electric apparatus comprising a substantially circular grid of conducting material provided with radial slots, and means for supporting the resultant sectors in substantially fixed relation to each other. a r

6. An electrode structure for vapor electric apparatus comprising a frame, supporting means therefor, and a plurality of perforated sectors of conducting material supported therefrom.

'Z. An electrode structure for vapor electric apparatus comprising a ring of refractory insulating material resting on the bottom thereof, a frame supported at the upper edge of said ring, anda plurality of perforated conducting sectors supported from said frame, said sectors coacting to cover substantially the entire space surrounded by said ring.

8. An electrode structure for vapor electric apparatus embodying a. closed container with a pool of cathode material in the lower portion thereof, and provided with an arclimiting refractory ring resting in said pool and projecting from the upper surface thereof, which comprises a frame supported from the upper portion-of said ring and a plurality of perforated conducting members Mill masses supported from said frame, said members coacting to cover substantially the entire.

cathode surface delimited by said ring. A

9. An electrode structure for vapor electric apparatus embodying a closed container having a pool of cathode material in the loWer portion thereof and provided with an arc-limiting refractory ring resting in said pool and projecting from the upper surface thereof, which comprises a frame supported from the upper portion of said ring, a pluraltit-y of perforated conducting members supported from said frame and coacting to Wltll said cathode pool, a conductive conn'ection from said starting electrode to said sectors, and means for maintaining an electromotive force between said keep-alive electrode and said cathode pool.

In testimony whereof, I have "hereunto subscribed myname this 25th day of April,

SIDNEY W. FARNSWORTlElQ 

